Here is search logs of 650,000 AOL users. It's very interesting to view search history of particular person and analyze his personality. Let's do it together! Read more about AOL search database scandal or view research papers on web searching.
www.db4o.com
Explicit
Open source object database for Java and .NET by Versant. Includes documentation, download option, benchmarks, and whitepapers. [Commercial, or free with GPL or dOCL for open source projects]